This invention relates to an improvement in a gas-metal-arc welding process by which the rate of metal deposition is increased. This process involves feeding a consumable electrode wire towards the weld deposit pool while a shielding gas is flowed around the end of the electrode and the arc gap between the electrode and the deposit pool. The shielding gas may comprise a mixture of major proportions of argon and helium and minor proportions of carbon dioxide and oxygen. The arc ionizes the gas to form a plasma field in the arc gap. Large droplets or globules are melted, one by one, from the free end of the wire electrode and are transferred by free-flight across the arc gap to the weld deposit pool located on a substrate.
My U.S. Pat. No. 4,463,243, issued Jul. 31, 1984, for a "Welding System" describes the welding process and the shielding gas mixture. The process is further described in my U.S. Pat. No. 4,866,246, issued Sep. 12, 1989, for a "High Rate Deposition Gas-Metal-Arc Welding Process" and, in U.S. Pat. No. 4,843,210, issued Jun. 27, 1989, for a "Downward Gas-Metal-Arc Welding Process" and, U.S. Pat. No. 4,572,942, issued Feb. 25, 1986for a "Gas-Metal-Arc Welding Process."
The process may be performed by utilizing a welding gun such as that disclosed in U.S. Pat. No. 4,464,560, issued Aug. 7, 1984, for an "Arc Welding Gun With Gas Diffuser and External Cooling Conduit" to John G. Church and Emerson G. Malone. Another suitable welding gun and its manner of utilizing this process are disclosed in U.S. Pat. No. 4,529,863, issued Jul. 16, 1985 for "Gas-Metal-Arc Welding Method."
As mentioned above, the process generally involves depositing a weld metal upon a substrate, such as metal plates to be welded together or the like, by feeding a wire electrode endwise towards a weld deposit pool located upon the substrate. Electrical energy is passed through the electrode wire and across the arc gap between the end of the wire and the pool. This causes droplets or globules to form, one by one, on the free end of the electrode and to melt off the electrode end. The drops, as they melt off the end of the electrode, freely move or transfer across the arc gap to the pool. Meanwhile, the shielding gas surrounds the electrode end and the moving droplets or globules and provides a heated plasma field in that area.
The formation and transfer of the droplets or globules takes place rapidly. That is, a droplet forms on the end of the electrode and its connection with the electrode body portion necks-down or narrows to the point where the drop disconnects from the end of the electrode to freely fly across the arc gap. After each drop disconnects from the electrode, the next drop forms and then disconnects from the electrode. As described in my above-mentioned U.S. Pat. No. 4,866,246, a relatively high voltage and amperage is used and the wire is rapidly fed towards the arc gap so that a large amount of molten metal is deposited in the weld deposit pool.
However, it is desirable to increase the deposit rate while not adversely affecting the quality of the weld bead or the welded joint. Thus, the present invention relates to an improvement in the foregoing process by which the drops are more rapidly disconnected or melted off the end of the electrode wire and are positively projected or propelled across the arc gap to the molten metal weld pool. Consequently, the rate that drops are formed is increased.